This application relates to a method of attaching a die, such as a switch, made of a first base material to a circuit board made of a second base material. An interposer having a coefficient of thermal expansion intermediate the first and second materials is used to reduce thermal stresses.
Circuit boards are utilized in various control applications. As one example, modern aircraft have many printed circuit boards providing various control functions. One known circuit board has a die attached to the circuit board, to provide a control function. As an example, an FET (field effect transistor) may provide On/Off switch and circuit breaker functions to a circuit on the circuit board.
In many applications the circuit board has a base, such as a polymer base, while the attached die may have a silicon base. When the two are attached together, there is a good deal of thermal stress between the two due to their differing coefficients of thermal expansion. As an example, if the two are soldered together, the solder absorbs the differential expansion and may crack. It has sometimes been challenging to provide such an assembly that is able to withstand expected thermal expansion over a wide temperature range.